Piston operated pumps for liquid carbon dioxide



Oct. 3, 1967 P. E. SCOVELL 3,344,746

PISTON OPERATED PUMPS FOR LIQUID CARBON DIOXIDE Original Filed Aug. 7,1964 INVENTOR avi /M %M ATTORNEYS United States Patent 3,344,746 PISTONOPERATED PUMPS FOR LIQUID CARBON DIOXIDE Peter Eric Scovell, SouthCroydon, England, assignor to The Distillers Company Limited, Edinburgh,Scotland, a British company Continuation of application Ser. No.388,205, Aug. 7, 1964. This application Dec. 22, 1966, Ser. No. 604,068Claims priority, application Great Britain, Aug. 21, 1963, 33,004/ 63 7Claims. (Cl. 103-153) This is a continuation of application Ser. No.388,205 filed Aug. 7, 1964, now abandoned.

This invention is concerned with improvements in or relating to pistonoperated pumps adapted to pump liquid carbon dioxide.

Piston operated pumps adapted to pump liquid carbon dioxide have beenknown for a number of years. These pumps are not entirely satisfactoryin that liquid carbon dioxide tends to leak from the pumping chamberbetween the piston and cylinder wall where, due to the sudden reductionin pressure, it changes to gas and solid. The presence of the solidcarbon dioxide between the piston and cylinder wall causes wear andunsatisfactory pumping action. The term cylinder wall used throughoutthis specification includes any surfaces encircling the piston, such asfor example sealing surfaces.

An object of the present invention is to provide an improved pistonoperated pump in which the disadvantage hereinbefore described is eitherreduced or eliminated.

Accordingly the present invention is a piston operated pump adapted topump liquid carbon dioxide wherein a device is provided which is capableof applying a gas under pressure to any liquid carbon dioxide whichleaks from the pumping chamber between the piston and cylinder wall,said pressure being sufiicient to prevent liquid carbon dioxide fromsolidifying between the piston and cylinder wall. 7

The device is preferably an annular recess in the wall of the cylinderbelow the piston head which forms a cavity in combination with thepiston and a passageway in the wall through which fluid under pressurecan be supplied to the cavity. A sealing gland or glands are preferablyprovided in this cavity which reduce the tendency for liquid carbondioxide to leak past the piston. The passageway which connects thiscavity and the outside of the cylinder can be formed by a hole boredthrough the cylinder wall. Gas can be supplied through this passagewayto the cavity to give a pressure sufiicient to prevent any liquid carbondioxide which leaks between the piston and the cylinder wall fromsolidifying.

Any pressure greater than the pressure at the triple point pressure ofany carbon dioxide which has leaked between the piston and cylinder wallis suitable. When the pump is operated at ambient temperatures asuitable pressure is between 200 and 800 pounds per square inch. This isthe pressure range under which liquid carbon dioxide is normally stored.Thus in a preferred embodiment the device is supplied with carbondioxide by connecting it to a container of liquid carbon dioxide, forexample the liquid carbon dioxide which it is desired to pump.

The preferred gas is carbon dioxide. When the device is an annularrecess in the cylinder wall as hereinbefore described the carbon dioxidecan be supplied to the cavity as a liquid where it forms the gas underpressure under the influence of the heat generated by the pump as soonas it is operated.

An embodiment of the present invention is illustrated in theaccompanying drawing which shows a longitudi- Patented Oct. 3, 1967 nalsection of a piston operated pump. The pump consists of a body 1 formedinternally into a cylinder with a cylinder wall 3 and a piston 2attached to a crank 4 within the cylinder. One end of the cylinder isformed into a pumping chamber 5 which is provided with an inlet valve 6and exit valve 7 to allow liquid carbon dioxide to enter and leave thepumping chamber. The cylinder wall is provided with an annular recess 8which forms a cavity 9 in combination with the piston. A gland 10 isprovided in this cavity at the end nearest to the pumping chamber. Thisgland forms a seal which reduces the amount of liquid carbon dioxideentering the cavity from the pumping chamber. A gland 11 is provided atthe other end of the cavity to prevent or retard the escape of carbondioxide gas from the cavity. A passageway 12 is formed between thecavity and the outside of the cylinder by a hole bored through thecylinder wall. This passageway allows gas under pressure to pass intothe cavity.

In operation when piston 2 is lowered liquid carbon dioxide is drawninto the pumping chamber 5 through an inlet valve 6 from a container inwhich it is stored under a gas pressure of approximately 300 pounds persquare inch. It is then forced out of the pumping chamber through outletvalve 7 when piston 2 is raised. During this reciprocating movement ofthe piston cavity 9 is pressurised to a pressure of 300 pounds persquare inch by carbon dioxide gas from the container. Any liquid carbondioxide which leaks from the pumping chamber 5 between the piston andcylinder wall past gland 10 is prevented from expanding to form solidcarbon dioxide by the pressure of carbon dioxide gas in cavity 9.

I claim:

1. A piston pump apparatus adapted to pump liquid carbon dioxide,comprising a cylinder member having a pumping chamber therein, a pistonmember reciprocally slidable within the cylinder member to pump fluidfrom the pumping chamber, the members having sizes such that liquidcarbon dioxide leaks from the chamber between the members, at least oneof said members having a cavity therein opening laterally against theother member, a source of gas under a pressure greater than the triplepoint pressure of the carbon dioxide being pumped, and conduit meanscoupling said source of gas and said cavity for applying the gas undersaid greater pressure to the space between the piston member and thecylinder member wall, whereby when said gas is supplied to the cavityand applied to the liquid carbon dioxide which leaks from the pumpingchamber between the piston member and the cylinder member Wall, it willprevent liquid carbon dioxide from solidifying between the piston memberand cylinder member wall.

2. A pump apparatus as claimed in claim 1 in which the cavity is anannular recess in the cylinder member wall below the piston member head,and said conduit means includes a passageway in the wall through whichthe gas under pressure can be supplied to the cavity.

3. A pump apparatus as claimed in claim 2 in which the cavity has asealing gland at the end thereof toward the piston member head whichreduces the tendency of liquid carbon dioxide to leak past the pistonmember.

4. A pump apparatus as claimed in claim 1 in which the source of gasunder pressure is a source of carbon dioxide.

5. A process for pumping liquid carbon dioxide which comprises supplyingliquid carbon dioxide to the pumping 6. A process as claimed in claim 5wherein the ap-' plied gas is carbon dioxide.

7. A process as claimed in claim 5 wherein the gas is carbon dioxideformed from liquid carbon dioxide under the influence of heat generatedby the pump when it is 5 operated.

References Cited UNITED STATES PATENTS Slate 6210 Seligmann 62-10 White103153 Prosser 103204 Tyree 103153 Yaindl 62-55 Loliger 103204 DONLEY I.STOCKING, Primary Examiner.

7/1921 Schlacks 230-203 10 HENRY F. RADUAZO, Examiner.

1. A PISTON PUMP APPARATUS ADAPTED TO PUMP LIQUID CARBON DIOXIDE,COMPRISING A CYLINDER MEMBER HAVING A PUMPING CHAMBER THEREIN, A PISTONMEMBER RECIPROCALLY SLIDABLE WITHIN THE CYLINDER MEMBER TO PUMP FLUIDFROM THE PUMPING CHAMBER, THE MEMBERS BEING SIZES SUCH THAT LIQUIDCARBON DIOXIDE LEAKS FROM THE CHAMBER BETWEEN THE MEMBERS, AT LEAST ONEOF SAID MEMBERS HAVING A CAVITY THEREIN OPENING LATERALLY AGAINST THEOTHER MEMBER, A SOURCE OF GAS UNDER A PRESSURE GREATER THAN THE TRIPLEPOINT PRESSURE OF THE CARBON DIOXIDE BEING PUMPED, AND CONDUIT MEANSCOUPLING SAID SOURCE OF GAS AND SAID CAVITY FOR APPLYING THE GAS UNDERSAID GREATER PRESSURE TO THE SPACE BETWEEN THE PISTON MEMBER AND THECYLINDER MEMBER WALL, WHEREBY WHEN SAID GAS IS SUPPLIED TO THE CAVITYAND APPLIED TO THE LIQUID CARBON DIOXIDE WHICH LEAKS FROM THE PUMPINGCHAMBER BETWEEN THE PISTON MEMBER AND THE CYLINDER MEMBER WALL, IT WILLPREVENT LIQUID CARBON DIOXIDE FROM SOLIDIFYING BETWEEN THE PISTON MEMBERAND CYLINDER MEMBER WALL.